a serial hybrid just means that the electrical power for the propulsion is made available by a second, in this case fuel burning piston, engine. The fuel engine could be much smaller and could run on cheap fuel in its most economic range .The Electric motor with its high torque could drive a large diameter slow turning propeller. 130 kW Motor, 40kwh buffer battery and a 120hp gasoline engine should do. As AVGAS prices are astronomically high over here and availability is uncertain for the future, i would highly appreciate this more efficient system, even if it would be more complex, expensive and heavier than the lycoming. Unfortunately its out of my first time builder capabilities. Did anyone try already?
Patrick
Ps please excuse the typos...